Ski or snowboard turns when moments are applied to the ski edge by skier body position in relation to ski slope and the skier speed, and the turning performance is determined by the centrifugal force and the reaction to this force introduced by ski-snow contact.
To achieve tight turning radius, the ski sideline edge is curved and ski is made flexible to allow bending during the turn and avoid rolling. To improve the experience of skiing, manufacturers introduced skis with strong sideline curvature—broader tip and tail and narrow center, and high flexibility.
Since such design leads to large vibration amplitudes, manufacturers produce skis with different stiffness factor to balance the needs and experience of broad range of skiing enthusiasts, from beginners to professionals. In effect, soft and highly flexible skis, targeting average expertise levels and/or soft snow have tendencies to vibrate excessively at high speeds or in tight turns or hard or icy snow, while less flexible or stiffer skis, targeted for experts are difficult to control by an average skilled user. However, all skis, regardless of their design parameters will vibrate in turns does loosing the edge contact with the snow making edge control difficult and increases discomfort and decreases safety and performance.
Depending on the speed and snow condition, ski vibrates at several bending and torsional frequencies with the amplitudes of such vibration dependent on ski construction—stiff and hard ski may have lower amplitudes at some frequencies but are difficult to control by an average user, while soft ski may be easy to control but have higher vibration amplitudes. In general, the ski bending frequencies are between 10 Hz and 100 Hz, while the torsional frequencies are in the range of 100 Hz to 150 Hz.
For several decades designers try different materials, manufacturing techniques and vibration damping schemes to somehow minimize its negative effect. As the ski vibrates predominantly at the front and the tail quarters of its length, various damping materials and structures were added to the front, tip and tail of the ski.
However, adding large amount of damping does not solve this problem while making ski less responsive and slow. It is well know that ski vibrates over relatively wide range of frequencies, and while dampening materials or dampening viscous structures are effective to damp particular frequency, such structures are not efficient in damping wide range of frequencies, and sometime even counterproductive. Ceramic piezoelectric structures were proposed to provide active dampeners, however, since only small amount of strain—as low as 1%, is usable to provide the control signal, they proved to be difficult to control and unstable or require “pre-tension” of the piezoelectric material in proportion to the expected bending forces in order to produce reference signal, and as such not compatible with ski manufacturing technologies.
Today smart-phones besides providing basic communication over cellular network is equipped with various input/output capabilities, such as wireless PAN (Personal Area Network), and provides significant computing resources. When such computing resources communicate with the remote sensors, such as MEMS accelerometers, magnetometers, gyroscopes, pressure sensors and actuators, the resulting system can provide various sport analytical tools for adaptive vibration control system for ski and snowboards.
By coupling MEMS accelerometers and thermo-electric actuators embedded in the ski equipment with a vibration analysis application residing in the user smart-phone, one can provide adaptive vibration control system for ski. Furthermore, using the smart-phone connectivity to the wireless cellular network, a real-time feedback to the predefined remote location may be provided, adding benefits in ski testing or training. The adaptive vibration control system described in this invention can operate using any of wireless technology such as: cdma2000, UMTS, WiMax, LTE. LTE-A, etc.